Abstract：
Nitrous acid (HONO) is a reactive gas that plays an important role in atmospheric chemistry. However, accurately quantifying its direct emissions and secondary formation in the atmosphere as well as attributing it to specific nitrogen sources remains a significant challenge. In this study, we developed a novel method using stable nitrogen and oxygen isotopes (δ15N; δ18O) for apportioning ambient HONO in an urban area in North China. The results show that secondary formation was the dominant HONO formation processes during both day and night, with the NO2 heterogeneous reaction contributing 59.0 ± 14.6% in daytime and 64.4 ± 10.8% at nighttime. A Bayesian simulation demonstrated that the average contributions of coal combustion, biomass burning, vehicle exhaust, and soil emissions to HONO were 22.2 ± 13.1, 26.0 ± 5.7, 28.6 ± 6.7, and 23.2 ± 8.1%, respectively. We propose that the isotopic method presents a promising approach for identifying nitrogen sources and the secondary formation of HONO, which could contribute to mitigating HONO and its adverse effects on air quality.
摘要：
亚硝酸（HONO）是一种反应性气体，在大气化学中起着重要作用。然而,准确量化其在大气中的直接排放和二次形成以及将其归因于特定的氮源仍然是一个重大挑战。在这项研究中,我们开发了一种使用稳定的氮和氧同位素（δ15N；δ18O）分配华北市区环境HONO的新方法。结果表明，次级形成是白天和黑夜中主要的HONO形成过程，NO2非均相反应在白天贡献59.0±14.6％，在夜间贡献64.4±10.8％。贝叶斯模拟表明，煤燃烧的平均贡献，生物质燃烧，汽车尾气,土壤对HONO的排放量分别为22.2±13.1、26.0±5.7、28.6±6.7和23.2±8.1％，分别。我们建议同位素方法为识别氮源和HONO的二次形成提供了一种有前途的方法，这可能有助于减轻HONO及其对空气质量的不利影响。
